The present invention relates to ventilation equipment, and more particularly, to an exhaust device used in a cleanroom for manufacturing semiconductor devices.
BACKGROUND OF THE INVENTION
In the semiconductor industry, the cleanliness requirement for a cleanroom has been becoming severer from year to year. Convenient references for cleanrooms are U.S. Pat. No. 4,693,173 to Saiki et al., and U.S. Pat. No. 5,553,496 to Nishiyama et al.
FIG. 1 illustrates a simplified diagram of separate cleanrooms 100 and 100xe2x80x2. Elements in room 100xe2x80x2 having a prime marker are analogous to the elements in room 100.
In cleanroom 100, air conditioning system 110 provides air flow 120 that goes substantially in a single direction, from ceiling 101 to room floor 102. Often, air conditioning system 110 establishes an over pressure in the cleanroom (so-called plenum system). Also, air conditioning system 110 can provide reuse of air (circulation outside room 100 from floor 102 to ceiling 101, through filter 112)
While a variety of wafer manufacturing facilities stand on floor 102, further service room 103 below floor 102 provides infrastructure, for example, by electrical cable 104 and pipe 106.
Having rooms 100 and 100xe2x80x2 separated is required because wafer processing machine 140 in room 100xe2x80x2 could influence wafer processing machine 130 in room 100 by chemicals that parasitically leak out from machine 140. This problem is now explained with more detail by way of example. Processing machine 130 of a first type processes wafer 139 by deep ultraviolet (DUV) lithography. This comprises the application of photoresist pattern, exposure by ultraviolet radiation, etching and other steps.
In a consecutive manufacturing step, processing machine 140 of a second type seals wafer 149 by dispersing IMID (polyimide) through nozzle 142. IMID is a liquid that is temporarily stored in tank 144 and transported in pipe 106xe2x80x2. Sometimes, for example, once a week, IMID-machine 140 with tank 144, pipe 106xe2x80x2 and nozzle 142 is cleaned (rinsed) by a solvent, for example, NMP (1Methyl-2Pyrrolidone,M-pyrol). NMP that is also a liquid easily converts into gas that becomes part of cloud 150 with exhaust gas. Exhaust gas containing NMP is detrimental to the processes in DUV-machine 130 because they would attack wafers 139 (still unsealed) being processed in DUV-machine 130.
Since cloud 150 leaves machine 140, there is a danger that room air flow 120xe2x80x2 contributes to the distribution of cloud 150 with exhaust gas throughout room 100xe2x80x2.
As explained, the prior art prevents contamination of processes by chemicals, (e.g., NMP interfering with the DUV processes) by providing separate cleanrooms 100 and 100xe2x80x2. The separation is, however, inconvenient and expensive. For example, the wafers have to be carried from room 100 to room 101xe2x80x2.
The present invention seeks to provide a means which mitigates or avoids these and other disadvantages and limitations of the prior art.